阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。
Johnny Carson began his work in television ____his twenties. First he worked at local stations in Nebraska. Several years ____ (late), he moved to Los Angeles, California. It was “The Tonight Show”____made Johnny Carson famous for thirty years. He became ____most popular star of American television. He ____(call) “the king of late night.” Critics said Americans from all parts of the country liked him and felt they knew him.
He did not take his fame ____ (serious). For example, when asked how he became a “star”, he answered: “I started in a gas state and I cooled.” Carson's special skill was his sense of humor. Audiences laughed at his jokes he made at the____ (begin) of his show. However, sometimes they laughed even____(hard) at the jokes that failed. He was the most____(power) performer (表演者) on television. Many comedians (喜剧演员) and singers became successful after____ (appear) on “The Tonight Show”.
向下推此物体，使物体加速下滑，斜面体依然和地面保持相对静止，则斜面体受地面的摩擦力 （ ）